Presently, levamisole, (S)-(-)-2,3,5,6-tetrahydro-6-phenylimidazo-[2,1-b]thiazole hydrochloride, is one of the few immunoregulants, or immunepotentiators, in the clinical literature. The clinical efficacy of levamisole in correcting an imbalance of immune homeostasis, and thus its effectiveness in treatment of a number of diseases and disorders characterized or complicated by an imbalance of immune homeostasis, has been confirmed by well-controlled multi-center clinical studies in several diseases and disorders. Consequently, compounds possessing therapeutic properties similar to or better than levamisole would be a valuable contribution to medicine in the field of immunology, or other fields as well. Accordingly, it is an important discovery that the N-substituted mercaptomethylacetamidines of the present invention possess immunological properties similar but superior to those of levamisole, and that they are thus of value in correcting an imbalance of immune homeostasis and for treatment of a number of diseases and disorders characterized or complicated by such an imbalance of immune homeostasis.